Bicycle Fork Having Lock-out, Blow-off, and Adjustable Blow-off Threshold

ABSTRACT

A bicycle fork includes a pair of fork leg assemblies, each of the leg assemblies having an upper leg telescopingly engaged with a lower leg. A damping assembly is provided in at least one of the legs. The damping assembly includes lock-out and blow-off compression circuits. These compression circuits are externally adjustable without tools. Furthermore, these two compression circuits may be adjusted independently of each other.

BACKGROUND AND SUMMARY OF THE INVENTION

1. Field of the Invention

The present invention is generally related to vehicle suspensionassemblies. More particularly, the present invention is related to afront suspension fork for use on an off-road bicycle.

2. Description of the Related Art

Suspension fork assemblies are often utilized on off-road bicycles, ormountain bikes, to absorb energy imparted to the front wheel by theterrain on which the bicycle is being ridden. The use of a suspensionfork allows a rider to traverse rougher terrain, at a greater speed andwith less fatigue in comparison to riding a bicycle equipped with arigid fork. Due to the fact that bicycle riders vary greatly in bothweight and riding ability, it is highly desirable that certainperformance aspects of the suspension fork, such as compression andrebound damping characteristics, be capable of adjustment to suit aparticular individual.

To avoid the need to disassemble the fork in order to adjust thesuspension settings, it is preferable to locate the adjustment controlssuch that they are externally accessible. Furthermore, an individualrider is likely to ride in wide variety of terrain conditions, oftenduring the course of a single ride or race. Accordingly, adjustment ofthe damping characteristics while riding is greatly facilitated bylocating the adjustment controls on an upper portion of the suspensionfork.

Ideally, the adjustment controls would be disposed on a damper capassembly at the top of one of the fork legs and include a compressionlock-out for substantially preventing compression of the fork. Thecompression lock-out feature is desirable so that the suspension forkmay selectively behave substantially as a rigid fork while riding onsmooth terrain, to enhance both handling and power transfer to the rearwheel of the bicycle. However, prior art mountain bike suspension forkshave failed to provide both a compression lock-out feature and externaldamping adjustment controls that are easily accessible while riding.Further, existing mechanisms for providing external damping adjustmentand compression lock-out require undue complexity. Thus, an improvedmountain bike suspension fork is desirable.

SUMMARY OF PREFERRED EMBODIMENTS

Preferred embodiments of the present suspension fork include a dampingassembly having a damping control assembly located at an upper portionof the fork. A hollow shaft connects a piston to the control assembly.On compression of the fork, damping fluid flows upward through thecentral passage of the shaft to the damping control assembly. With sucha fluid flow arrangement, a simplified arrangement of externallyaccessible controls may be disposed on the control assembly. Thisarrangement permits compression damping, rebound damping and compressionlock-out controls to be collectively located so as to be accessible to arider of a bicycle, while the bicycle is being ridden.

In addition, a reservoir is preferably disposed in a lower portion ofthe fork such that fluid exiting the damping control assembly travels ina downward direction due to gravity, substantially the entire length ofthe fork. This arrangement advantageously allows the damping fluid toalso lubricate certain internal components of the fork, includingbushings, seals and a suspension coil spring, if provided.

A preferred embodiment comprises a bicycle front fork including an uppertube having a top portion, a bottom portion and an intermediate portion.A lower tube having a top portion, a bottom portion and an intermediateportion is telescopingly movable with respect to the upper tube. Anupper control assembly is positioned at the top portion of the uppertube. A damping cartridge is positioned at least partly within the lowertube and defines a top portion, a bottom portion and an intermediateportion. At least a section of the lower tube surrounding the cartridge,at least partially defines a reservoir. A shaft extends from the topportion of the upper tube into the damping cartridge. A main dampingpiston is connected to the shaft and positioned in the cartridge. Atleast the bottom portion of the cartridge defines a lower internalchamber located below the piston. The piston, the shaft and the controlassembly cooperate to define a flow channel from the chamber through thepiston, the shaft and the control assembly to the reservoir.

A preferred embodiment comprises a bicycle front fork including an uppertube having a top portion, a bottom portion and an intermediate portion.A lower tube having a top portion, a bottom portion and an intermediateportion is telescopingly movable with respect to the upper tube. Anupper control assembly is positioned at the top portion of the uppertube. A damping cartridge is positioned at least partly within the lowertube and defines a top portion, a bottom portion and an intermediateportion. At least a section of the lower tube surrounding the cartridge,at least partially defines a reservoir. The bottom portion of thedamping cartridge defines a lower control assembly which operates topermit fluid to enter the cartridge from the reservoir through the lowercontrol assembly, but prevents fluid from exiting the cartridge at lowpressure levels. A shaft extends from the top portion of the upper tubeinto the damping cartridge. A main damping piston is connected to theshaft and positioned in the cartridges At least the bottom portion ofthe cartridge defines a lower internal chamber located below the piston.The piston, the shaft and the control assembly cooperate to define aflow channel from the chamber through the piston, the shaft and thecontrol assembly to the reservoir. The upper control assembly includes aone-way valve which prevents the flow of fluid from the reservoirthrough the control assembly when the shaft and the piston move upwardaway from the bottom portion of the damping cartridge.

A preferred embodiment comprises a bicycle front fork including an uppertube having a top portion, a bottom portion and an intermediate portion.A lower tube having a top portion, a bottom portion and an intermediateportion is telescopingly movable with respect to the upper tube. Anupper control assembly is positioned at the top portion of the uppertube. A damping cartridge is positioned at least partly within the lowertube and defines a top portion, a bottom portion and an intermediateportion. At least a section of the lower tube surrounding the cartridge,at least partially defines a reservoir. A shaft extends from the topportion of the upper tube into the damping cartridge. A main dampingpiston is connected to the shaft and positioned in the cartridge. Atleast the bottom portion of the cartridge defines a lower internalchamber located below the piston. The piston, the shaft and the controlassembly cooperate to define a flow channel from the chamber through thepiston, the shaft and the control assembly to the reservoir. The uppercontrol assembly also includes a lock-out valve which selectivelyprevents the flow of fluid from the shaft through the assembly and tothe reservoir.

A preferred embodiment comprises a bicycle front fork including an uppertube having a top portion, a bottom portion and an intermediate portion.A lower tube having a top portion, a bottom portion and an intermediateportion is telescopingly movable with respect to the upper tube. Anupper control assembly is positioned at the top portion of the uppertube. A damping cartridge is positioned at least partly within the lowertube and defines a top portion, a bottom portion and an intermediateportion. At least a section of the lower tube surrounding the cartridge,at least partially defines a reservoir. A shaft extends from the topportion of the upper tube into the damping cartridge. A main dampingpiston is connected to the shaft and positioned in the cartridge. Atleast the bottom portion of the cartridge defines a lower internalchamber located below the piston. The piston, the shaft and the controlassembly cooperate to define a flow channel from the chamber through thepiston, the shaft and the control assembly to the reservoir. A blow-offvalve is positioned at the bottom portion of the cartridge to permitflow through the blow-off valve and into the reservoir in response to athreshold blow-off pressure.

A preferred embodiment comprises a bicycle front fork including an uppertube having a top portion, a bottom portion and an intermediate portion.A lower tube having a top portion, a bottom portion and an intermediateportion is telescopingly movable with respect to the upper tube. A shaftextends axially from the top portion of the upper tube. A main dampingpiston is connected to the shaft and at least partially defines adamping chamber. The fork defines a low speed compression circuit and arebound circuit. A control assembly located at the top portion of theupper tube includes a first control connected to the low speedcompression circuit and is manually adjustable, external of the fork. Ina first position, fluid is able to flow through the low speedcompression circuit and, in a second position, flow through said lowspeed compression circuit is prevented. A second control is connected tothe rebound circuit and is manually adjustable, from external of thefork. In a first position, a first rate of flow through the reboundcircuit is permitted and, in a second position, a second rate of flowthrough the rebound circuit is permitted. The first rate of flow ishigher than said second rate of flow. The control assembly alsocomprises a third control connected to a restrictor, which communicateswith the low speed compression circuit. The restrictor is manuallymovable from external of the fork between at least a first position,wherein the restrictor provides at least a first amount of resistance toflow through the low speed compression circuit, and a second position,wherein the restrictor provides a second amount of resistance to flowthrough the low speed compression circuit.

A preferred embodiment comprises a bicycle front fork including an uppertube having a top portion, a bottom portion and an intermediate portion.A lower tube having a top portion, a bottom portion and an intermediateportion is telescopingly movable with respect to the upper tube. A shaftextends, axially from the top portion of the upper tube. A main dampingpiston is connected to the shaft and at least partially defines adamping chamber. The fork defines a low speed compression circuit. Acontrol assembly located at the top portion of the upper tube includes afirst control connected to the low speed compression circuit and ismanually adjustable, external of the fork. In a first position, fluid isable to flow through the low speed compression circuit and, in a secondposition, flow through said low speed compression circuit is prevented.The control assembly also comprises a second control connected to arestrictor, which communicates with the low speed compression circuit.The restrictor is manually movable from external of the fork between atleast a first position, wherein the restrictor provides at least a firstamount of resistance to flow through the low speed compression circuit,and a second position, wherein the restrictor provides a second amountof resistance to flow through the low speed compression circuit.

A preferred embodiment comprises a shock absorber including an uppertube having a top portion, a bottom portion and an intermediate portion.A lower tube having a top portion, a bottom portion and an intermediateportion is telescopingly movable with respect to the upper tube. Anupper control assembly is positioned at the top portion of the uppertube. A damping cartridge is positioned at least partly within the lowertube and defines a top portion, a bottom portion and an intermediateportion. At least a section of the lower tube surrounding the cartridge,at least partially defines a reservoir. A shaft extends from the topportion of the upper tube into the damping cartridge. A main dampingpiston is connected to the shaft and positioned in the cartridge. Atleast the bottom portion of the cartridge defines a lower internalchamber located below the piston. The piston, the shaft and the controlassembly cooperate to define a flow channel from the chamber through thepiston, the shaft and the control assembly to the reservoir.

A preferred embodiment comprises a bicycle having a front fork. Thefront fork includes an upper tube having a top portion, a bottom portionand an intermediate portion. A lower tube having a top portion, a bottomportion and an intermediate portion is telescopingly movable withrespect to the upper tube. An upper control assembly is positioned atthe top portion of the upper tube. A damping cartridge is positioned atleast partly within the lower tube and defines a top portion, a bottomportion and an intermediate portion. At least a section of the lowertube surrounding the cartridge, at least partially, defines a reservoir.A shaft extends from the top portion of the upper tube into the dampingcartridge. A main damping piston is connected to the shaft andpositioned in the cartridge. At least the bottom portion of thecartridge defines a lower internal chamber located below the piston. Thepiston, the shaft and the control assembly cooperate to define a flowchannel from the chamber through the piston, the shaft and the controlassembly to the reservoir.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned and other features will now be described withreference to the drawings of preferred embodiments of the presentsuspension fork. The illustrated embodiments of the suspension fork areintended to illustrate, but not to limit the invention. The drawingscontain the following figures:

FIG. 1 is a perspective view of a bicycle having a preferred embodimentof a front wheel suspension fork;

FIG. 2 is a perspective view of the suspension fork of FIG. 1, which isillustrated as removed from the bicycle;

FIG. 3 is a cross-section of the suspension fork of FIG. 1, thusillustrating the internal components of the fork;

FIG. 4 is an enlarged cross-section illustrating the rebound dampingcircuit of the suspension fork of FIG. 1;

FIG. 5 is an enlarged cross-section of a rebound adjustment cap assemblyof the suspension fork of FIG. 1;

FIG. 6 is a cross-section of the cap assembly taken along the line 6-6in FIG. 5;

FIG. 7 is an enlarged cross-section of a base valve assembly of thesuspension fork of FIG. 1;

FIG. 8 is an enlarged cross-section of a rebound adjustment and lock-outcap assembly of a second embodiment of a suspension fork;

FIG. 9 is a cross-section of the cap assembly of FIG. 8, taken along theline 9-9 in FIG. 8;

FIG. 10 is a cross-section of a base valve assembly of the secondembodiment.

FIG. 11 is a cross-section of a rebound adjustment, low speedcompression adjustment and lock-out cap assembly of a third embodimentof a suspension fork;

FIG. 12 is a top view of a low-speed compression adjustment knob of thecap assembly of FIG. 11;

FIG. 13 is a cross-section of the low-speed compression adjustment knobof FIG. 12, taken along the line 13-13 of FIG. 12;

FIG. 14 is a cross-section of a blow-off adjustment base valve assemblyof the third embodiment;

FIG. 15 is a cross-section of a coil-sprung embodiment having a coilspring in each leg for providing an expansion force on the fork;

FIG. 16 is a cross-section of the coil-sprung fork of FIG. 15 in ashortened travel position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates an off-road bicycle, or mountain bike 20, including aframe 22 which is comprised of a main frame portion 24 and a swing armportion 26. The swing arm portion 26 is pivotally attached to the mainframe portion 24. The bicycle 20 includes front and rear wheels 28, 30connected to the main frame 24. A seat 32 is connected to the main frame24 in order to support a rider of the bicycle 20.

The front wheel 28 is supported by a preferred embodiment of asuspension fork 34 which, in turn, is secured to the main frame 24 by ahandlebar assembly 36. The rear wheel 30 is connected to the swing armportion 26 of the frame 22. A rear shock 38 is positioned between theswing arm 26 and the frame 22 to provide resistance to the pivotingmotion of the swing arm 26. Thus, the illustrated bicycle 20 includessuspension members between the front and rear wheels 28, 30 and theframe 22 which operate to substantially reduce wheel impact forces frombeing transmitted to the rider of the bicycle 20.

FIG. 2 illustrates the suspension fork 34 detached from the bicycle 20of FIG. 1. The suspension fork 34 includes right and left legs 40, 42,as referenced by a person in a riding position on the bicycle 20. Theright leg 40 includes a right upper tube 44 telescopingly received in aright lower tube 46. Similarly, the left leg 42 includes a left uppertube 48 telescopingly received in a left lower tube 50. A crown 52connects the right upper tube 44 to the left upper tube 48 therebyconnecting the right leg 40 to the left leg 42 of the suspension fork34. In addition, the crown supports a steerer tube 54, which passesthrough, and is rotatably supported by, the frame 22 of the bicycle 20.The steerer tube 54 provides a means for connection of the handlebarassembly 36 to the suspension fork 34, as illustrated in FIG. 1.

Each of the right lower tube 46 and left lower tube 50 includes a dropout 56 for connecting the front wheel 28 to the fork 34. An arch 58connects the right lower tube 46 and the left lower tube 50 to providestrength and minimize twisting thereof. Preferably, the right lower tube46, left lower tube 50 and the arch 58 are formed as a unitary piece,however, the tubes 46, 50 and arch 58 may be separate pieces andconnected by a suitable fastening method.

The suspension fork 34 also includes a pair of rim brake bosses 60 towhich a standard rim brake may be mounted. In addition, the fork 34 mayinclude a pair of disc brake bosses 62 to which a disc brake may bemounted. Of course, the suspension fork 34 may include only one or theother of the rim brake bosses 60 and disc brake bosses 62, depending onthe type of brake system desired.

FIG. 3 is a cross-section view of the suspension fork 34 of FIG. 2having the front portion cutaway to illustrate various internalcomponents of the fork 34. As described previously, each of the uppertubes 44, 48 is capable of telescopic motion relative to its respectivelower tube 46, 50. Each of the fork legs 40, 42 includes an upperbushing 64 and a lower bushing 66 positioned between the respectiveupper tubes 44, 48 and the lower tubes 46, 50. The bushings 64, 66inhibit wear of the upper tubes 44, 48 and the lower tubes 46, 50 bypreventing direct contact between the tubes. Preferably, the bushings64, 66 are fixed to the respective lower tubes 46, 50 and are made froma self-lubricating and wear resistant material, as is known in the art.However, the bushings 64, 66 may be similarly fixed to the upper tubes44, 48. Preferably, the bushings 64, 66 include grooves (not shown)which allow hydraulic fluid to pass between the bushings 64, 66 and theupper fork tubes 44, 48.

Each of the lower tubes 46, 50 have a closed lower end and an open upperend. Each of the upper tubes 44, 48 is received into a respective lowertube 46, 50 through its open upper end. A sealing arrangement isprovided on each leg 40, 42 at the location where the upper tubes 44, 48enter the open end of the lower tubes 46, 50. The sealing arrangementcomprises a main seal 68, preferably disposed above a foam ring 70. Themain seals 68 are supported by the lower tubes 46, 50 and are in sealingengagement with the upper tubes 44, 48 to substantially prevent oil fromexiting, or foreign material from entering, the fork legs 40, 42 betweenthe open end of the lower tubes 46, 50 and the upper tubes 44, 48. Thefoam rings 70 are supported by the lower tubes 46, 50 and are inengagement with the upper tubes 44, 48 to capture hydraulic fluid whichpasses upward between the upper bushings 64 and upper fork tubes 44, 48.The foam rings 70 then distribute the hydraulic fluid evenly onto theupper tubes 44, 48 which, in turn, lubricate the main seals 68.

Each of the fork legs 40, 42 includes a bottom-out bumper 72 disposed atthe closed lower end of the lower tubes 46, 50. The bottom-out bumpers72 serve to prevent direct contact between the upper tubes 44, 48 andthe lower tubes 46, 50 when the fork 34 is in a fully compressedposition. Accordingly, the bottom-out bumpers 72 are preferably made ofan energy absorbing material, such as an elastomer or rubber.

The illustrated suspension fork 34 includes both a suspension springassembly 74 and a damper assembly 76. The suspension spring assembly 74provides resistance to compression of the fork 34 and releases energystored during compression to cause the fork 34 to extend, or rebound.The damper assembly 76 provides a damping force which resists bothcompression and rebound motion, to slow the motion of the suspensionfork 34 in either direction, as is known. Preferably, the damperassembly 76 is contained within the right leg 40 of the suspension fork34, while the suspension spring assembly 74 is contained within the leftleg 42.

The suspension spring assembly 74 comprises a spring cap assembly 80which closes the upper end of the left upper tube 48. A seal 81 providesa preferably air and fluid-tight seal between the cap assembly 80 andthe inner surface of the left upper tube 48. A spring piston rod 84extends vertically upward from the closed lower end of the lower leftfork tube 50 and supports a spring piston 86. The piston 86 includes aradial through-hole 85 which corresponds with a through-hole 87 in thepiston rod 84. A pin 89 is press fit into the through-holes such that itengages the piston 86 on both sides of the piston rod 84 to secure thepiston 86 thereto. The spring cap assembly 80 is fixed for movement withthe left upper tube 48 and the spring piston 86 is fixed for movementwith the left lower tube 50.

The spring piston 86 is in sealing engagement with the inner surface ofthe left upper tube 48. The cap assembly 80 and piston 86 define apositive air spring chamber 88 between them. A positive air valve 90allows communication with the positive air spring chamber 88. A standardhigh pressure pump may be attached to the positive air valve 90 in orderto pressurize the positive air spring chamber 88. Thus, whenpressurized, the positive air spring chamber 88 acts as a suspensionspring and exerts an extension force on the suspension fork assembly 34.A cap 91 is preferably threaded onto the valve 90 to provide protectionfrom damage and keep foreign matter away from the valve 90.

A lower spring plate 92 is held within a counter bore of the upper forktube 48 by a snap ring 93. An upper spring stop 95 is fixed in an axialposition on the spring piston rod 84 by a pin 97, in a manner similar tothe piston 86, as described above. A negative spring chamber 94 isdefined between the lower spring plate 92 and upper spring stop 95. Anouter negative spring 96 and an inner negative spring 98 are placedwithin the negative spring chamber 94. Preferably, the outer spring 96and inner spring 98 are coil-type springs arranged concentrically witheach other and with the spring piston rod 84. A pair of spring guides 99assist in keeping the springs 96, 98 concentric with the piston rod 84and from contacting the inner surface of upper tube 48 when compressed.

The spring plate 92 includes an central aperture 101 which providesclearance for the spring piston rod 84 to pass through. A small amountof lubricating fluid, preferably approximately 30 cc's of a suitablehydraulic damping fluid, is provided in the left fork leg 42 tolubricate the seal 68, bushings 64, 66, negative springs 96, 98 andspring guides 99.

Desirably, the outer negative spring 96 is of a greater length than theinner negative spring 98. Preferably, the spring rates of the outer andinner negative springs 96, 98 are selected such that the inner negativespring 98 is near its free-length when the suspension fork 34 iscompressed by substantially only the weight of a rider of the bicycle20. Although the illustrated negative spring assembly comprises a dualcoil spring arrangement, a single negative spring may also be used. Inaddition, an air spring arrangement similar to the positive air springchamber 88 may also be used in place of the coil-type negative springarrangement.

As described above, the damper assembly 76 is preferably housed withinthe right leg 40 of the suspension fork 34. The damper assembly 76 ispreferably an open-bath, cartridge-type damper having a cartridge tube100 fixed to the closed lower end of the right lower tube 46 andextending vertically upward. A damper shaft 102 extends verticallydownward from a damper cap assembly 104 and supports a rebound dampingassembly 106 on its lower end. Thus, the rebound damping assembly 106 isfixed for movement with the right upper tube 44 while the cartridge tube100 is fixed for movement with the right lower tube 46.

The rebound damping assembly 106 is positioned within the cartridge tube100 and is in telescoping engagement with the inner surface of thecartridge tube 100. A cartridge tube cap 108 closes the upper end of thecartridge tube and is in sealing engagement with the damper shaft 102.Thus, the cartridge tube defines a substantially sealed internalchamber, which contains the rebound damping assembly 106.

The rebound damping assembly 106 divides the interior of the cartridgetube 100 into a rebound chamber 110 above the rebound damping assembly106 and a compression chamber 112 below the rebound damping assembly106. A reservoir 114 is defined between the outer surface of thecartridge tube 100 and the inner surfaces of the right upper and lowertubes 44, 46. A base valve assembly 116 allows selective communicationbetween the compression chamber 112 and the reservoir 114.

The damper assembly 76 also includes a rebound adjust rod 118 whichextends vertically downward from the damper cap assembly 104 within thecentral passage of the damper shaft 102. An upper compression passage120 is defined between the rebound adjust rod 118 and the inner surfaceof the damper shaft 102. The upper compression passage 120 allowscommunication between the compression chamber 112 and the damper capassembly 104, as will be described in detail below.

FIG. 4 is an enlarged cross-section of the rebound damping assembly 106.As described above, a cartridge tube cap 108 closes the cap end of thecartridge tube 100. An outer seal 122 creates a seal between thecartridge tube cap 108 and the cartridge tube 100 while an inner seal124 creates a seal between the cartridge tube cap 108 and the dampershaft 102. Accordingly, extension and retraction of the damper shaft 102is permitted while maintaining the rebound chamber 110 in asubstantially sealed condition. The seals referred to herein maycomprise O-rings or other suitable seals known to those of skill in theart. In addition, a bushing 125 is press fit into the cartridge tube cap108 to prevent direct contact between the cap 108 and damper shaft 102.

A rebound piston support shaft 126 is fixed within the lower opening ofthe damper shaft 102 and includes a seal 128 to prevent fluid frompassing therebetween. Preferably, the rebound piston support shaft 126and the damper shaft 102 are connected by a roll-crimping method.Specifically, an annular recess 127 is provided on the outer surface ofthe support shaft 126. The damper shaft 102 is substantially cylindricaland is positioned on the support shaft 126 such that it overlaps theannular recess 127. A roll-crimping machine rotates the damper shaft 102and support shaft 126 assembly while it mechanically deforms the dampershaft 102 material into the recess 127 (as illustrated in FIG. 4),thereby securing the support shaft 126 to the damper shaft 102. Asroll-crimping is known in the art, further description is not deemednecessary in order to practice the invention. While a roll-crimpingprocess is preferred, other suitable methods may also be used to jointhe support shaft 126 to the damper shaft 102.

A tubular piston rod extension 130 is fixed to the rebound adjust rod118 by a threaded fastener 132. A lower portion of the piston rodextension 130 includes external threads which mate with internal threadsof the rebound piston support shaft 126. Rotation of the rebound adjustrod 118 also rotates the piston rod extension 130 and results in axialmovement of the piston rod extension 130 relative to the rebound pistonsupport shaft 126. Upward axial movement of the damper shaft 102uncovers a bleed port 134, which extends radially through the reboundpiston support shaft 126, while downward axial movement of the dampershaft 102 covers the bleed port 134.

A rebound piston 136 is fixed to the lowermost end of the rebound pistonsupport shaft 126 by a hollow piston bolt 138. The hollow passage of thepiston bolt 138, along with the hollow passage of the piston rodextension 130 define a lower compression passage 140, which is in fluidcommunication with the compression chamber 112. The upper end of thepiston rod extension 130 includes an aperture, or transfer port 142,which allows fluid communication between the upper compression passage120 and the lower compression passage 140, as indicated by the arrow Fin FIG. 4. Thus, fluid is able to flow from the compression chamber 112,through the lower compression passage 140 and upper compression passage120, to the damper cap assembly 104.

A lower end of the rebound piston support shaft 126 includes a shoulder144 which provides a support surface for a spacer 146. The spacer 146engages the piston 136 to distance the piston 136 away from the shoulder144. A rebound piston seal 148 creates a seal between the rebound piston136 and the inner surface of the cartridge tube 100, thereby definingthe rebound chamber 110 above the piston 136 and the compression chamber112 below the rebound piston 136. The rebound piston 136 includes acompression port 150 and a rebound port 152 extending substantiallyaxially through the radially outer portion of the rebound piston 136.

A check valve assembly 156 is arranged on the upper surface of therebound piston 136 to selectively allow fluid communication from thecompression chamber 112 to the rebound chamber 110 through thecompression port 150. The check valve 156 includes a check plate 158biased into an engagement with the upper surface of the piston 136 by acheck spring 160. The check plate 158 is substantially annular in shapeand capable of sliding axially with respect to the spacer 146. The checkspring 160 is preferably a flat helical spring having a relatively lowspring constant such that the spring 160 biases the check plate 158 intocontact with the upper surface of the piston 136 to seal the compressionport 150 during rebound motion, but easily compresses such that thecheck plate 158 moves away from the piston 136 to allow fluid flowthrough the compression port 150 in response to compression motion ofthe suspension fork 34.

A rebound shim stack 162 is secured to the lower surface of the reboundpiston 136 by the piston bolt 138. The rebound shim stack 162 may asingle shim, or a stack comprised of multiple shims, which aresubstantially annular in shape and made from a flexible spring steel, asis known in the art. The rebound shim stack 162 selectively allows fluidcommunication between the rebound chamber 110 and the compressionchamber 112 through the rebound port 152. During compression motion ofthe suspension port assembly 34, the rebound shim stack 162 is engagedwith the lower surface of the piston 136 to prevent fluid from flowingthrough the rebound port 152. During rebound motion of the suspensionfork assembly 34, the rebound shim stack 162 acts as a diaphragm springand flexes in response to a sufficient force of fluid pressure in therebound chamber 110, to allow fluid flow through the rebound port 152and into the compression chamber 112.

A bleed port 163 extends axially through the cartridge tube cap 108between the seal 124 and the bushing 125. The bleed port 163 is sizedsuch that air bubbles within the hydraulic fluid of the rebound chamber110 can escape, without allowing an appreciable amount of fluid to passtherethrough. Advantageously, this construction prevents a loss ofincompressibility of the fluid within the rebound chamber 110.

FIG. 5 is an enlarged cross-section of the upper control assembly, ordamper cap assembly 104. The suspension fork 34 of FIGS. 1-7 utilizes adamper cap assembly 104 including a rebound adjustment control, as willbe described in detail below.

The rebound adjust rod 118 and damper shaft 102 extend downward from thedamper cap assembly 104 and define the upper compression passage 120between them. As also described above, the damper cap assembly 104closes the upper end of the right upper tube 44. A cap seal 164 createsa seal between the damper cap assembly 104 and the inner surface of theright upper tube 44. The rebound adjust rod 118 extends upward throughthe center of the damper cap assembly 104 and is fixed for rotation witha rebound adjustment knob 166 by a threaded fastener 168. A rod seal 170creates a seal between the rebound adjust rod 118 and a central passageof the damper cap assembly 104.

The damper cap assembly 104 is comprised primarily of a cap body 172 anda shaft support 174. The damper shaft 102 is roll-crimped to the shaftsupport 174 with a seal 176 preventing fluid flow therebetween. Externalthreads on the upper portion of the shaft support 174 mate with internalthreads of an internal channel of the cap body 172 and secure acompression piston 178 and compression shim stack 180 therebetween.

The shim stacks disclosed herein are preferably comprised of one or moreannular shims, preferably made from thin steel, as is known to those ofskill in the art. Each individual shim acts as a diaphragm spring whichpossesses an inherent spring rate when deflected about its central axis.As is known, a plurality of shims may be used to achieve a desiredspring rate. The shims making up a single shim stack may vary indiameter, preferably with the largest diameter shim being locatedimmediately adjacent the surface defining the ports through which theshim stack is controlling flow. For example, if a shim stack utilizingmultiple diameter shims is used with the above-described damper capassembly 104, preferably the largest diameter shim is locatedimmediately adjacent lower surface of the compression piston 178.

The compression piston 178 is axially spaced from the cap body 172 by ashoulder 182 to create a compression chamber 184 between the uppersurface of the piston 178 and the lower surface of the cap body 172.Preferably the shoulder 182 is integral with the cap body 172. A seal iscreated between the outer radial surface of the compression piston 178and the cap body 172 by a piston seal 186.

With reference to FIGS. 5 and 6, the shaft support 174 includes radiallyextending ports 188 which allow fluid communication between the uppercompression passage 120 and an annular transfer chamber 189 definedbetween the shaft support 174 and the shoulder 182. Radial passages inthe shoulder 182 allow fluid communication between the transfer chamber189 and the compression chamber 184. Thus, the radial ports 188 andradial passages 190 cooperate with the transfer chamber 189 to allowfluid communication between the upper compression passage 120 and thecompression chamber 184. Advantageously, the transfer chamber 189 allowsfluid communication between the radial ports 188 and radial passages 190despite their relative angular positions. Thus, as illustrated in FIG.6, it is not necessary that the radial ports 188 and radial passages 190be aligned, because the transfer chamber 189 permits fluid flow to bedirected therebetween. This feature enhances manufacturability andreduces cost because a threaded connection between the cap body 172 andshaft support 174 maybe used.

The compression piston 178 includes a low speed compression port 192 anda plurality of mid-speed compression ports 194 passing axiallytherethrough. As illustrated in FIG. 6, the mid-speed compression ports194 are disposed at a first radial distance D1 from a center axis A ofthe piston 178 while the low-speed compression ports are located asecond radial distance D2 from the axis A. Preferably, the distance D1is less than the distance D2. As a result, fluid flowing through the lowspeed compression port 192 has more leverage on the compression shimstack 180 in comparison to fluid flowing through the mid-speedcompression port 194 and, accordingly, fluid flow is allowed through thelow speed compression port 192 at a lower fluid pressure than isrequired to open the mid-speed compression ports 194. Advantageously,this arrangement provides separate low and mid-speed damping circuits,while remaining compact and without adding undesired weight.

One or more high-speed compression ports 195 (illustrated in phantom)may be provided and be of a smaller diameter or located a smaller radialdistance D3 from the axis A, or a combination thereof, than themid-speed compression ports 194. Such a construction would allow thehigh-speed compression ports to be relatively inactive at low andmid-speed shaft motion, while providing the primary damping force athigh-speed shaft motion. Thus, it will be appreciated by one of skill inthe art, that a plurality of port diameters and radial locations fromthe axis A may be used to achieve desired damping forces at specificshaft speeds. Also, as illustrated, a combination of ports may be usedto provide varying damping forces over a range of shaft speeds.

With reference to FIG. 5, the damper cap assembly 104 also includes aball detent assembly 196. The ball detent assembly 196 comprises aspring 198 placed between a set screw 200 and a ball bearing 202 to biasthe ball bearing 202 into engagement with one of a plurality ofrecesses, or detents 204, formed on the rebound adjust rod 118. Thespring rate of the spring 198 is selected such that the biasing force ofthe spring 198 may be easily overcome so that the rebound adjustmentknob 166 may be turned by hand, while also providing positive feedbackas to the relative position of the rebound adjust rod 118. Preferably,four (4) detents 204 are equally spaced around the circumference of therebound adjust rod 118. Also, the rebound adjust rod 118 is desirablycapable of rotating approximately three (3) revolutions between itsupper position and its lower position. Accordingly, twelve (12) distinctrebound damping positions are defined by the rebound adjust rod 118 andthe ball detent assembly 196.

FIG. 7 is an enlarged cross-section of the lower control assembly, orbase valve assembly 116. The base valve assembly 116 allows selectivecommunication between the reservoir 114 and the compression chamber 112.The base valve assembly 116 generally comprises a valve body 206, a shimbolt 208 and a check shim 210. A lower portion of the shim bolt 208includes external threads which mate with internal threads of the basevalve body 206. The shim bolt 208 includes a shaft portion 212 whichcenters the substantially annular check shim 210 with respect thereto.The shim bolt 208 also includes a shoulder portion 214 of largerdiameter than the shaft portion 212 such that the check shim 210 iscapable of limited axial movement between the upper surface of the basevalve body 206 and a shoulder portion 214 of the shim bolt 208.

A check spring 213 biases the check shim 210 into engagement with thetop surface of the base valve body 206. Preferably, the spring 213 is aconical coil spring having a low spring rate and small wire diameter sothat it allows the check shim 210 to move easily away from the topsurface of the base valve body 206. The small end of the spring 213engages the base valve body 206 while the large end engages the checkshim 210. Alternatively, a low axial travel shim without a spring may beused.

The radial outer portion of base valve body 206 also includes aplurality of refill ports 216 which pass axially therethrough. When thefluid pressure in the compression chamber 112 is greater than the fluidpressure in the reservoir 114, the check spring 213 keeps the check shim210 engaged with the top surface of the base valve body 206, thusclosing off the axial refill ports 216 and effectively preventing theflow of fluid therethrough. However, when the fluid pressure in thereservoir 114 is greater than the fluid pressure in the compressionchamber 112, the check shim 210 moves away from the base valve body 206,against the small biasing force of the spring 213, to allow fluid flowfrom the reservoir 114 to the compression chamber 112, through therefill ports 216. Advantageously, the configuration and spring rate ofthe check spring 213 allows the check shim 210 to move easily away fromthe top surface of the base valve body 206 in order to prevent flowrestriction which could result in cavitation, but also returns the checkshim 210 quickly into engagement with the base valve body on compressionmovement of the fork 34.

The suspension fork assembly 34 described in relation to FIGS. 1-7 iscapable of both compression, where the upper tubes 44, 48 and the lowertubes 46, 50 move closer together relative to each other and rebound,wherein the upper tubes 44, 48 and the lower tubes 46, 50 move fartherapart in relation to each other. A fully compressed position is definedwherein the suspension fork 34 is compressed such that the lower-mostsurfaces of the upper tubes 44, 48 come to rest against the pair ofbottom-out bumpers 72. A fully extended position is defined when theupper tubes 44, 48 are retracted from the lower tubes 46, 50 such thatthe outer and inner negative springs 96, 98 are fully compressed betweenthe negative spring chamber seal 92 and the spring piston 86.

A ride height of the suspension fork assembly 34 is defined as therelative position between the upper tubes 44, 48 and the lower tubes 46,50 when the suspension fork 34 is bearing the weight of a rider of thebicycle 20, with substantially no other external forces being present.As mentioned above, the ride height is preferably such that the innernegative spring 98 is substantially near its free length, or itsuncompressed length, when no other external force is exerted on thespring. The ride height can be adjusted to suit riders of differentweights by tuning the positive air spring chamber 88 and/or the outerand inner negative springs 96, 98. Air can be added or removed from thepositive air spring chamber 88 to adjust the pressure therein. The freelength and/or spring rate of the outer and inner negative springs 96, 98may also be selected to achieve the desired ride height.

When the suspension fork 34 is in compression, such as when the frontwheel 28 of the bicycle 20 encounters a bump, the air within thepositive air spring chamber 88 functions as an air spring toprogressively resist compression of the upper tubes 44, 48 into thelower tubes 46, 50. The outer and inner negative springs 96, 98 exert acompressive force on the suspension fork 34 and thereby assist theinitial compressive motion between the upper tubes 44, 48 and the lowertubes 46, 50. Advantageously, with such a construction, the negativesprings 96, 98 help to overcome any static friction present in thesuspension fork 34, due to the bushings and various seals, in order toallow initial compression with a minimal force input.

With reference to FIGS. 3-7, the above-described damper assembly 76includes various flow paths which provide damping to the motion of thesuspension fork 34 in both a compression and a rebound direction. Thevarious flow paths can be generally categorized into compressioncircuits and rebound circuits. Of course, some passages may be utilizedfor both compression and rebound fluid flow. Desirably, the damperassembly 76 includes a sufficient volume of a suitable damping fluidsuch that at least the entire cartridge tube 100, upper and lowercompression passages 120, 140 and damper cap assembly 104 may be filled,and enough damping fluid remains in the reservoir 114 to cover therefill ports 216 of the base valve assembly 116.

During compression motion of the suspension fork 34, the rebound piston136 moves downward in relation to the cartridge tube 100 and, as aresult, the fluid pressure within the compression chamber 112 increases.In response to the increased pressure in the compression chamber 112,hydraulic fluid contained therein passes through the check valveassembly 156 of the rebound piston 136 to the rebound chamber 110. Asdescribed above, the check spring 160 that biases the check plate 158against the top surface of the rebound piston 136 desirably has a lowspring rate and therefore offers little resistance to fluid flow throughthe compression ports 150. Thus, fluid flow from the compression chamber112 to the rebound chamber 110 through the check valve 156 servesprimarily to fill the rebound chamber 110 and, desirably, provideslittle damping force.

Also in response to the increased pressure in the compression chamber112, fluid flows in an upward direction from the compression chamber 112into the lower compression passage 140. A portion of the fluid flowsfrom the lower compression passage 140 through the bleed port 134 andinto the rebound chamber 110. As with the flow of fluid through thecheck valve 156, the flow of fluid through the bleed port 134 servesprimarily to fill the rebound chamber 110 and, preferably, does notprovide a substantial damping force.

The remainder of the fluid continues to flow upward in the lowercompression passage 140 and into the upper compression passage 120through the transfer port 142. With reference to FIG. 5, the flow offluid continues to travel upward through the upper compression passage120 and into the damper cap assembly 104. The flow of fluid then travelsthrough both the radial port 188 of the shaft support 174 and the radialpassage 190 of the piston shoulder 182 and into the compression chamber184, thus increasing the fluid pressure therein.

As described above, because the low speed compression port 192 ispositioned further radially outward in comparison to the plurality ofmid-speed compression ports 194, the compression shim stack 180 isdeflected from the lower surface of the compression piston 178 at lowerfluid pressures than is necessary to deflect the shim stack 180 to openthe mid-speed compression ports 194. Thus, the primary damping force isprovided by the flow through the low speed compression port 192 which isresisted by the compression shim stack 180 at low fluid pressures whichcorrespond with low speed compressive motion.

As the compressive motion speed increases and therefore, fluid pressurewithin the compression chamber 184 increases, sufficient fluid pressureis created to deflect the compression shim stack 180 such that fluid isable to flow through the mid-speed compression ports 194. At thesecompression speeds, the primary damping force as provided by the fluidflow through the mid-speed compression ports 194 which is resisted bythe compression shim stack 180.

Hydraulic fluid that exits through either the low speed or mid-speedcompression ports 192, 194 flows downward, due to gravity, to fill thelower portion of the reservoir 114. In addition, because the damperassembly 76 is an open bath system, hydraulic fluid within the reservoir114 is also able to move throughout the reservoir 114 and,advantageously, provides lubrication for the bushings 64, 66 and variousseals within the damper assembly 76.

On rebound motion of the suspension fork 34, the rebound piston 136moves in an upward direction with respect to the cartridge tube 100,thereby increasing the pressure in the rebound chamber 110. In responseto the increase in fluid pressure within the rebound chamber 110, fluidflows through the bleed port 134 and downward through the lowercompression passage 140 and then to the compression chamber 112. Asdescribed above, the rebound adjustment knob 166 may be rotated to inturn rotate the rebound adjust rod 118 and cause the piston rodextension 130 to increase or decrease the exposed portion of the bleedport 134. In this manner, the damping force provided by the restrictedflow of fluid through the bleed port 134 may be adjusted.Advantageously, because the rebound adjustment knob 166 is disposed onthe damper cap assembly 104, it may be easily manually adjusted by therider of the bicycle 20, even while riding. In addition, no tools arenecessary to change the damping rate and such adjustment may be madeexternally, without requiring disassembly of the suspension fork 34.

Also in response to the increased pressure with the rebound chamber 110,fluid flows through the rebound port 152 and, if the fluid pressure isgreater than a predetermined threshold, deflects the rebound shim stack162 away from the bottom surface of the rebound piston 136 to allowfluid to flow from the rebound chamber 110 to the compression chamber112. Rebound damping force is provided by the rebound shim stack 162against the flow of fluid through the rebound port 152.

The suspension fork 34 additionally includes a refill feature whichoperates to refill the compression chamber 112 during rebound motion.During rebound, the compression shim stack 180 within the damper capassembly 104 creates a substantially air-tight seal with the lowersurface of the compression piston 178. As a result, the low pressurecondition in the compression chamber 112 is not able to suction fluidfrom within the upper compression passage 120. This ensures that theupper compression passage 120 and damper cap assembly 104 remain filledwith fluid. Advantageously, the upper compression passage 120 andcompression chamber 184 do not have to be refilled upon subsequentcompression motion of the suspension fork 34 before producing a dampingforce. In addition, upon extension and, therefore, upward movement ofthe rebound piston 136 relative the cartridge tube 100, the seal betweenthe compression shim stack 180 and the compression piston 178 serves todraw fluid from the reservoir 114 and into the compression chamber 112through the base valve assembly 116.

FIGS. 8-10 illustrate relevant portions of an alternative embodiment ofa suspension fork, generally indicated by the reference character 34′.Suspension fork 34′, in addition to having an adjustable rebound dampingcircuit, features a high-speed compression circuit (or blow-off) and alow/mid-speed compression lock-out. In most other respects, suspensionfork 34′ is similar in both construction and function to the suspensionfork 34 of FIGS. 1-7. Accordingly, like components will be indicatedwith like reference numerals, except that a (′) will be added.

With reference to FIG. 8, the central passage of the cap body 172′ isincreased in diameter to accommodate a lock-out cylinder 218 positionedbetween the cap body 172′ and the rebound adjust rod 118′. A seal 220provides a substantially fluid and air-tight seal between the lock-outcylinder 218 and the inner surface of the central passage of the capbody 172′. Additionally, cap seal 164′ provides a seal between therebound adjust rod 118′ and the inner surface of a central passage ofthe lock-out cylinder 218, rather than between the rebound adjust rod118 and the cap body 172, as in the previous embodiment.

The lock-out cylinder 218 includes a externally threaded portion 222which mates with the internal threads of the cap body 172′. Accordingly,rotation of the lock-out cylinder 218 results in corresponding axialmovement of the lock-out cylinder 218 with respect to the cap body 172′.Preferably, the mating threads of the cap body 172′ and the lock-outcylinder 218 are 10 mm diameter by 1 mm pitch, double-start threads.With such a construction, relatively large axial motion is achieved witha relatively small degree of rotation of the lock-out cylinder 218.

A blocking sleeve 224 extends in a downward direction from, and ispreferably unitary with, the lock-out cylinder 218. The blocking sleeve224 is configured to selectively allow fluid to pass, or substantiallyprevent fluid from passing, from the upper compression passage 120′ tothe compression chamber 184′. The lower end of the blocking sleeve 224is configured to mate with a blocking sleeve seat 226 of the shaftsupport 174′.

An upper-most, or “open”, position of the lock-out cylinder 218 isdefined when the blocking sleeve 224 is retracted such that the radialports 188′ of the shaft support 174′ and the radial passages 190′ of thepiston shoulder 182′ are substantially fully open, thereby allowingfluid to flow from the upper compression passage 120′ to the compressionchamber 184′ (reference FIG. 6). Conversely, a lower-most, or “closed”,position of the lock-out cylinder 218 is defined when the blockingsleeve 224 is advanced such that the radial ports 188′ and radialpassages 190′ are substantially fully closed, thereby substantiallyprohibiting the flow of fluid from the upper compression passage 120′ tothe compression chamber 184′. Desirably, the lock-out cylinder 218 movesbetween its open and closed positions with less than one revolution,preferably, with less than one-half revolution and, most preferably,with less than one-third revolution. The lock-out can be actuated morequickly and easily by the rider when the amount of rotation between theopen and closed position is relatively small.

With reference to FIGS. 8 and 9, a lock-out knob 228 is engaged with theupper portion of the lock-out cylinder 218 and is supported for rotationon the cap body 172′ by a ball bearing arrangement 230. A plurality ofball bearings 232 travel within an annular recess 234 (FIG. 8) definedby the cap body 172′ and are secured in recess 234 by a plurality of setscrews 236. The set screws 236 each have a substantially cone-shapedlower end 238 which engages one of the plurality of ball bearings 232.Thus, the lock-out knob 228 is secured in an axial position with respectto the cap body 172′ while being capable of rotation with respectthereto.

As described above, the lock-out cylinder 218 engages the upper portionof the lock-out knob 228. As illustrated in FIG. 9, the mating portionsof the lock-out cylinder 218 and the lock-out knob 228 each have ahex-shaped cross-section thereby fixing the lock-out cylinder 218 forrotation with the lock-out knob 228. Simultaneously, the lock-outcylinder 218 is able to move axially with respect to the lock-out knob228 by sliding motion between the hex-shaped cross-sections.

The lock-out knob 228 also includes a lever portion 240 which provides aconvenient surface for a rider of the bicycle 20 (FIG. 1) to grasp inorder to rotate the lock-out knob 228. The lever portion 240 alsoprovides a leverage advantage to increase the ease with which thelock-out knob 228 may be rotated.

With reference to FIG. 10, a preferred base valve assembly 116′ for usein conjunction with the damper cap assembly 104′ described immediatelyabove. In addition to the refill function of the base valve assembly 116of the suspension fork 34 of FIGS. 1-7, the present base valve assembly116′ includes a blow-off circuit 242. The blow-off circuit 242selectively allows fluid flow from the compression chamber 112′ to thereservoir 114′ at high compressive fluid pressures or shaft speeds.Preferably, the blow-off circuit 242 remains closed at compressive fluidpressures below the threshold necessary to open the low and mid-speedcompression circuits of the suspension fork 34′.

The blow-off compression circuit 242 generally comprises a valve opening244, a blow-off piston 246 and a blow-off spring 248. The valve opening244 is defined by a central passage of the shim bolt 208′ and includes ablow-off piston seat 250. The blow-off spring 248 is supported on aspring support shaft 252 and biases the blow-off piston into engagementwith the blow-off piston seat 250 to substantially prevent fluid frompassing through the valve opening 244 at fluid pressures below apredetermined threshold. This threshold is determined by a combinationof the spring rate of the blow-off spring 248, the preload on the spring248 and the area of the blow-off piston 246 that is subject to fluidpressure from the compression chamber 112. When fluid pressure in thecompression chamber 112′ is above the predetermined threshold, thepiston 246 is forced away from the piston seat 250 and allows fluid toflow through the valve opening 244 and through radial ports 254 in thebase valve body 206′ into the reservoir 114′, thus lowering the pressurewithin the compression chamber 112.

When the lock-out knob 228 is positioned such that the lock-out cylinder218 is at closed position, the flow of hydraulic fluid is preventedthrough the low, mid and high-speed compression circuits and thesuspension fork 34′ is in a locked-out state, where substantially norelative motion is permitted between the upper fork tubes 44, 48 and thelower fork tubes 46, 50 (FIG. 2). Advantageously, this prevents riderpedal energy from being absorbed by the suspension fork 34 therebyallowing such energy to instead promote forward motion of the bicycle 20(FIG. 1). If a large bump is encountered, such that the pressure withinthe compression chamber rises above the threshold necessary to open theblow-off valve 242, the valve 242 operates to allow fluid flow from thecompression chamber 112′ to the reservoir 114′. Advantageously, thisprevents damage to the various seals of the suspension fork 34′ andprevents the entire force of the bump from being transferred to therider.

The placement of the lock-out knob 228 on the damper cap assembly 104′allows easy access to the rider of the bicycle 20 (FIG. 1), even whileriding. This is advantageous because a wide variety of terrain may beencountered in a single ride such that “on-the-fly” (while riding)actuation of the lock-out knob 228 is highly desirable. Furthermore,because the low, mid and high-speed compression circuits are locked-outwithin the damper cap assembly 104′, the lock-out cylinder 218 remainsmechanically simple and compact, thereby decreasing the likelihood offailure, saving weight and reducing the cost of manufacture incomparison to lock-out assemblies located in the middle or lower regionof the fork leg, which often require complex actuation mechanisms.

FIGS. 11-14 illustrate relevant portions of another embodiment of asuspension fork, generally indicated by the reference character 34″.Suspension fork 34″, in addition to having an adjustable rebound dampingcircuit, a blow-off circuit and a low/mid-speed compression lock-out ofthe previously described suspension forks 34, 34′, respectively,includes adjustable low-speed compression damping and blow-off pressure.In most other respects, suspension fork 34″ is similar in bothconstruction and function to the suspension fork 34 and 34′ of FIGS. 1-7and 8-10, respectively. Accordingly, like components will be indicatedwith like reference numerals, except that a (″) will be added.

The damper cap assembly 104″ includes a low-speed compression dampingadjustment assembly 256, which generally comprises a low-speedcompression adjustment knob 258, an adjustment needle 260 and a needlespring 262. The adjustment needle 260 is supported for axial movementwithin a needle aperture 264, which extends axially through the cap body172″, and above the low speed compression port 192″. A seal 266 providesa seal between the adjustment needle 260 and the cap body 172″.

The adjustment needle 260 includes an annular flange, or needle stop268, which interferes with the cap body 172″ to define the upper mostposition of the adjustment needle 260 with respect to the compressionpiston 178″. In its uppermost position, a lower tapered end 270 of theadjustment needle 260 preferably does not substantially interfere withfluid flow through the low-speed compression port 192″. The needle stop268 also functions as an engagement surface for the needle spring 262,which is positioned between the needle stop 268 and the upper surface ofthe compression piston 178″ to bias the adjustment needle 260 into itsuppermost position. A lowermost position of the adjustment needle 260 isdefined when the needle 260 is force in a downward direction, overcomingthe biasing force of the needle spring 262, by the low-speed compressionknob 258, as will be described below. In its lowermost position, thetapered end 270 of the needle 260 is positioned within the low-speedcompression port 192″ to substantially inhibit fluid flow therethrough.In this manner, the damping force at low shaft speeds is increased. Ifdesired, the needle 260 may be configured to seat with the low-speedcompression port 192″ in its lowermost position, thereby effectivelypreventing fluid flow through the low-speed compression port 192″.

The low speed compression adjustment knob 258 is positioned between thelock-out knob 228″ and the cap body 172″ for rotation with respect tothe cap body 172″. The adjustment knob 258 engages the adjustment needle260 to move the needle 260 between its uppermost and lowermostpositions. The adjustment knob 258 includes an arcuate needle adjustmentchannel 272 (FIGS. 12 and 13), which extends radially about a centralaxis of the adjustment knob 258 for a specified angle θ. Desirably, theangle is between 90 and 180° Preferably, the angle is approximately144°. This range provides a desirable amount of adjustment while keepingthe rotation of the adjustment knob 258 small enough to be comfortableto actuate while riding.

The upper surface of the channel 272 defines a needle ramp surface 274,which is inclined relative to the upper surface of the compressionpiston 178″. An engagement surface 276 (FIG. 11), defined by the upperportion of the adjustment needle 260, engages the ramp surface 274 ofthe adjustment knob 258 such that rotation of the adjustment knob 258moves the adjustment needle 260 substantially between its uppermost andlowermost positions. Each end of the channel 272 defines a stop surface278, which interferes with the upper end of the adjustment needle 260 todefine the limits of the range of motion for rotation of the adjustmentknob 258. Preferably, a vertical distance V (FIG. 13) between theshallowest end of the ramp surface 274 and the deepest end of the rampsurface 274 is approximately 0.10 inches. Accordingly, the height of thetapered end 270 of the adjustment needle 260 varies by 0.10 inches withrespect to the upper surface of the compression piston 178″ when theadjustment knob 258 is rotated through its full range of motion.

The adjustment knob 258 additionally includes a ball detent mechanism280, which is similar in both structure and operation to the detentmechanism 196″ associated with the rebound adjust rod 118″. The balldetent mechanism 280 includes a ball bearing 282 which is biased intoengagement with one of a plurality of detents 284, defined by theadjustment knob 258, by a spring 286. Both the ball bearing 282 and thespring 286 are contained within a spring pocket 288, which is defined bythe cap body 172″. Preferably, nine (9) detents are provided throughoutthe range of motion of the adjustment knob 258, thereby providing nine(9) positive reference positions, which define individual settings ofthe low-speed compression adjustment assembly 256.

The adjustment knob 258 also includes an annular flange which defines afinger grip portion 290. The outer peripheral surface of the finger gripportion 290 includes a plurality of recesses 292, which preferablyextend entirely around the finger grip portion 290. The recesses 292provide an interrupted surface, which permits the adjustment knob 258 tobe easily rotated, even in muddy or wet conditions.

Advantageously, the construction of the damper cap assembly 104″ allowsthe level of low-speed compression damping to be adjusted externally,without necessitating disassembly of the suspension fork 34″. Inaddition, the level of low-speed compression damping may be adjustedon-the-fly. This provides an important advantage if the terrainconditions change over the course of a ride, or race, or if it turns outthat the initial setting was less than desirable.

With reference to FIG. 14, a preferred base valve assembly 116″ isillustrated for use in conjunction with the damper cap assembly 104″described immediately above. In addition to the refill function and theblow-off circuit 242, the present base valve assembly 116″ of FIG. 14includes a blow-off adjustment assembly 294.

To provide the capability of adjusting the blow-off circuit, theblow-off spring support shaft 262″ extends through an open end 296 ofthe base valve body 206″. The support shaft 262″ includes an externallythreaded portion 298, which mates with internal threads 300 of the basevalve body 206″. With this construction, rotation of the blow-off springsupport shaft 262″ is converted to axial movement of the support shaft262″ in relation to the base valve body 206″. Axial movement of thesupport shaft 262″ varies the relaxed length of the blow-off spring248″, and thereby varies the preload on the spring 248″. The preload ofthe blow-off spring 248″ influences the threshold fluid pressure withinthe compression chamber 112″ which is necessary to open the blow-offvalve 242″. More preload raises the threshold pressure, while lesspreload decreases the threshold pressure.

A blow-off adjustment knob 302 is secured to the lower, exposed end ofthe support shaft 262″ by a set screw 304. The adjustment knob 302allows the support shaft to be rotated easily by hand. A seal 305creates a seal between the support shaft 262″ and the base valve body206″ to substantially inhibit fluid from passing therebetween.

The blow-off adjustment assembly 294 also includes a ball detentassembly 306, which is similar to the ball detent assemblies describedabove. The ball detent assembly 306 includes a ball bearing 308 biasedinto engagement with a detent 310 defined by the support shaft 262″ by aspring 312. The ball bearing 308 and spring 312 are secured within acavity 314 by a set screw 316. Preferably, four (4) detents 310 areprovided and the support shaft 262″ is capable of making three (3)revolutions, thereby defining twelve (12) blow-off damping adjustmentpositions.

Advantageously, the suspension fork 34″ described immediately aboveprovides a wide range of both compression and rebound adjustment.Low-speed compression, rebound damping, blow-off pressure, as well as acompression lock-out feature, may all be accessed, and adjusted,externally and without the use of any tools. In addition, the low-speedcompression and rebound damping circuits, and lock-out, controls areconveniently located on the upper portion of the suspension fork 34″. Asa result, “on-the-fly” access to the above-mentioned controls isprovided, thereby permitting damping adjustment and actuation of thelock-out feature while the bicycle 20 (FIG. 1) is being ridden. Such aconstruction provides a distinct advantage by allowing initial dampingsettings to be adjusted, and the lock-out feature actuated, during thecourse of a ride or race.

FIGS. 15 and 16 illustrate a coil-sprung embodiment of the suspensionfork, indicated generally by the reference character 34′″. Suspensionfork 34′″ is similar in both construction and function to the previouslydescribed suspension forks 34, 34′ and 34″. Accordingly, like componentswill be indicated with like reference numerals, except that a (′″) willbe added.

The coil-sprung fork 34′″ utilizes a pair of positive coil springs toprovide an expansion force on the fork 34′″. A first spring 320 islocated in the right fork leg 40′″, along with the damper assembly 76′″,while a second spring 322 is located in the left leg 42′″, in place ofthe air spring arrangement of the previous embodiments. When suspensionaction is of primary concern, rather than the overall weight of the forkassembly, a pair of coil springs may be advantageous. With a coil spring320, 322 located in each of the fork legs 40′″, 42′″, respectively, theexpansion force on the fork 34′″ is more equally balanced between thefork legs 40′″, 42′″. This enhances the coaxial telescopic motion of theupper legs 44′″, 48′″ relative to the lower legs 46′″, 50′″ duringcompression and rebound for smooth motion with reduced binding.

The first spring 320 is positioned in the right leg 40′″ between thedamper cap assembly 104′″ and the cartridge tube cap 108′″. A pair ofspacers, including a first spacer 324 and a second spacer 326, areinterposed between the damper cap assembly 104′″ and the first spring320. The spacers 324, 326 are preferably substantially C-shaped so thatthey may be easily removed from the damper shaft 102′″ in a radialdirection. Desirably, the spacers 324, 326 are configured to engage thedamper shaft 102′″ in a snap fit arrangement.

A spring guide 328 is positioned between the spring 320 and the spacerimmediately adjacent the spring 320 (spacer 326 in the illustratedembodiment) to assist in keeping the spring 320 concentric with thedamper shaft 102′″. The cartridge tube cap 108′″ functions as a springguide for the lower end of the first spring 320. However, a separatespring guide member may also be provided.

The second spring 322 is positioned in the left leg 42′″ between thespring cap assembly 80′″ and the upper spring stop 95′″. A first spacer324 and a second spacer 326 are positioned between the spring capassembly 80′″ and the spring 322. Desirably, the first and secondspacers 324, 326 are substantially identical to the spacers describedabove in relation to the first spring 320.

A preload adjuster assembly 330 is desirably provided to allowadjustment of the preload on the second spring 322. The preload adjusterassembly 330 generally comprises an adjuster cap 332, an adjuster shaft334, a barrel 336 and an adjuster knob 338. The cap 332 is sealinglyengaged with upper open end of the upper tube 48′″. The cap 332 includesa central aperture which allows the adjuster shaft 334 to pass through,preferably in a sealed arrangement. The adjuster knob 338 is fixed tothe adjuster shaft 334 by fastener 340 such that rotation of theadjuster knob 338 results in rotation of the adjuster shaft 334. A balldetent assembly 341, substantially similar to those described above, maybe provided between the cap 332 and the adjuster knob 338 to define aplurality of preload adjustment positions.

The barrel 336 is threadably engaged with the adjuster shaft 334 andengages the upper most spacer 326. In addition, the barrel 336 includesa ball pocket for holding a ball bearing 342, which rides within anaxial groove 344 defined by the adjuster cap 332. This arrangementprevents the barrel 336 from rotating relative to the adjuster cap 332.Accordingly, rotation of the adjuster shaft 334, via the adjuster knob338, results in translation of the barrel 336 relative to the adjustercap 332. A change in the axial position of the barrel 336 alters thepreload force on the spring 322.

The upper spring stop 95′″ is roll-crimped to a plunger rod 346 whichextends upward from the closed end of the lower fork tube 50′″. Theupper stop 95′″ includes an o-ring 348 which serves as a spring guidefor the lower end of the spring 322. The o-ring 348 is preferred becauseit's compressibility allows a single size of o-ring to accommodate anumber of different spring inner diameters. The inner diameter of aspring may vary with different spring rates, therefore, the o-ring 348allows a number of springs 322 having varying spring rates to be usedwith the fork 34′″. A negative spring chamber 94′″ is defined betweenthe upper spring stop 95′″ and the lower spring stop 92′″. A singlenegative spring 96′″ is provided, rather than the dual negative coilspring arrangement of previous embodiments.

The fork assembly 34′″ of FIGS. 15 and 16 is capable of being adjustedfor varying amounts of travel, or total distance between it's fullycompressed and fully extended positions. With reference to FIG. 16, thefork 34′″ has been configured to have less travel than the fork 34′″ asconfigured in FIG. 15. To accomplish this, the spacers 324, 326 of theleft leg 42′″ were moved from their position between the upper end ofthe spring 322 and the spring cap assembly 80′″ to a position below theplunger rod 346. Specifically, the upper spring guide 99′″ is sliddownward on the plunger rod 346 and the spacers 324, 326 are positionedbetween the upper spring guide 99′″ and the upper spring stop 95′″. Thislowers the upper tubes 44′″, 48′″ relative to the lower tubes 46′″, 50′″and shortens the travel of the fork 34′″ by the combined length of thespacers 324, 326. In order to accommodate the shorter travelconfiguration without altering the preload on the first compressionspring 320, the spacers 324, 326 (FIG. 15) are removed from the rightfork leg 40.

Preferably, the first spacer 324 is approximately 20 mm in length andthe second spacer 326 is approximately 25 mm in length. The travel ofthe fork 34′″ as configured in FIG. 15 is approximately 125 mm. Asconfigured in FIG. 16, the travel is reduced to 80 mm. Alternatively,only one of the spacers 324, 326 may be positioned below the upperspring stop 95′″ while the other spacer remains positioned above thespring 324. With this configuration, the fork travel would be shortenedby the length of the spacer positioned below the upper spring stop 95′″,either 20 mm or 25 mm. The corresponding spacer 324, 326 would beremoved from the right fork leg 40, to maintain the desired preload onthe spring 320, as described above. Additionally, varying spacerconfigurations could be used. For example, the spacers 324, 326 could bereplaced by a single spacer. Also, spacers of other lengths may be used,as can readily be determined by one of skill in the art.

Although this invention has been described in terms of certainembodiments, other embodiments apparent to those of ordinary skill inthe art are also within the scope of this invention. Thus, variouschanges and modifications may be made without departing from the spiritand scope of this invention. In addition, various combinations of thepreferred embodiments are possible. For example, any of the base valveassemblies may be used in conjunction with any of the damper capassemblies, if desired.

Additionally, various arrangements of the damper and suspension springelements may be used. For example, the damper assembly and springassembly may be contained within a single leg of the fork, with theother leg being substantially empty. Further, the fork could configuredto have a single fork leg, with both the damper and suspension springelements being arranged within the single leg. Also, the fork may beconfigured for use with other vehicles, such as a road bicycle ormotorcycle, for example. Accordingly, the scope of the invention isintended to be defined only by the appended claims.

1. A method of operating a bicycle fork having lock-out and blow-offfeatures, including the step of adjusting a threshold pressure at whichthe blow-off feature operates during compression of the fork, theadjustment step being performed from a location external of the fork andwithout tools.
 2. A method of making a bicycle fork, including the stepsof: a) providing the fork with a lock-out valve; b) providing the forkwith a blow-off valve having a threshold pressure during compression ofthe fork at which the blow-off valve opens and allows fluid flow therethrough; c) providing the fork with the ability for its user to maketool-less adjustments of the threshold pressure from a location externalof the fork.
 3. A bicycle fork, comprising: first and secondtelescopingly engaged tubes configured to move closer together duringcompression of the fork; an adjustable lock-out valve, the lock-outvalve having a plurality of operator-selectable positions, one of theoperator-selectable positions of the lock-out valve at leastsubstantially inhibiting the first and second tubes from moving closertogether when subjected to a compressive forces less than anoperator-selectable threshold pressure; a manually adjustable blow-offvalve capable of tool-less adjustment from a location external of thefork, the blow-off valve allowing the first and second tubes to movecloser together in response to a pressure imparted on the valve duringcompression of the fork being equal to or greater than theoperator-selectable threshold pressure when the lock-out valve is in itssubstantially inhibiting movement position.
 4. A bicycle front fork,comprising: a compression fluid chamber configured to decrease in volumeduring at least a portion of the compression of the fork; a lock-outvalve, the lock-out valve in fluid communication with the compressionfluid chamber, and being adjustable between at least two operatingmodes; wherein: (a) in a first operating mode, fluid flow from thecompression fluid chamber is substantially unrestricted by the lock-outvalve, and (b) in a second operating mode, fluid flow from thecompression fluid chamber is at least partially blocked by the lock-outvalve; a first external adjuster permitting adjustment of the lock-outvalve between at least the two operating modes from a location externalof the fork; a blow-off valve associated with the compression fluidchamber, the blow-off valve allowing fluid flow from the compressionfluid chamber in response to the pressure in the chamber being equal toor greater than a threshold pressure during compression of the fork; anda second external adjuster, the second external adjuster permittingadjustment of the threshold pressure from a location external of thefork; whereby adjustments to the threshold pressure may be made withouttools.